Common Stock - Narrative (Details) - USD ($)		12 Months Ended
	Jun. 15, 2016	Apr. 30, 2018	Apr. 30, 2017
Class of Stock [Line Items]
Proceeds from June 2016 Public Offering	$ 4,300,000	$ 0	$ 4,340,000
Payments of issuance costs	$ 742,000
Issuance of common stock for services		$ 37,000	$ 44,000
Common Stock
Class of Stock [Line Items]
Issuance of registered shares (in shares)	2,000,000
Share Price	$ 2.25
Issuance of common stock (in shares)		8,569	18,564
Issuance of common stock for services		$ 22,500	$ 43,040
Over-Allotment Option | Common Stock
Class of Stock [Line Items]
Issuance of registered shares (in shares)	258,749